Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan.
Physiol Rep. 2021 May;9(9):e14842. doi: 10.14814/phy2.14842.
Mechanistic target of rapamycin complex 1 (mTORC1) plays a central role in muscle protein synthesis and repeated bouts of resistance exercise (RE) blunt mTORC1 activation. However, the changes in the proteolytic signaling when recurrent RE bouts attenuate mTORC1 activation are unclear. Using a RE model of electrically stimulated rat skeletal muscle, this study aimed to clarify the effect of repeated RE bouts on acute proteolytic signaling, particularly the calpain, autophagy-lysosome, and ubiquitin-proteasome pathway. p70S6K and rpS6 phosphorylation, indicators of mTORC1 activity, were attenuated by repeated RE bouts. Calpain 3 protein was decreased at 6 h post-RE in all exercised groups regardless of the bout number. Microtubule-associated protein 1 light chain 3 beta-II, an indicator of autophagosome formation, was increased at 3 h and repeated RE bouts increased at 6 h, post-RE. Ubiquitinated proteins were increased following RE, but these increases were independent of the number of RE bouts. These results suggest that the magnitude of autophagosome formation was increased following RE when mTORC1 activity was attenuated with repeated bouts of RE.
雷帕霉素靶蛋白复合物 1（mTORC1）在肌肉蛋白合成中发挥核心作用，反复进行抗阻运动（RE）会使 mTORC1 激活钝化。然而，当反复的 RE 运动使 mTORC1 激活减弱时，蛋白水解信号的变化尚不清楚。本研究使用电刺激大鼠骨骼肌的 RE 模型，旨在阐明反复 RE 运动对急性蛋白水解信号的影响，特别是钙蛋白酶、自噬溶酶体和泛素-蛋白酶体途径。mTORC1 活性的指标 p70S6K 和 rpS6 的磷酸化在重复 RE 运动后被减弱。无论重复次数如何，所有运动组在 RE 后 6 小时时钙蛋白酶 3 蛋白均减少。微管相关蛋白 1 轻链 3 亚基β-II，自噬体形成的指标，在 RE 后 3 小时增加，在 RE 后 6 小时重复增加。RE 后泛素化蛋白增加，但这些增加与 RE 重复次数无关。这些结果表明，在 mTORC1 活性被反复的 RE 运动钝化时，RE 后自噬体形成的幅度增加。
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